The study of gene fusions began more than 30 years ago, when the Philadelphia chromosome in chronic myeloid leukemia (CML) was shown to result in a BCR–ABL1 chimera and the MYC gene was found to be deregulated through fusions with immunoglobulin-encoding genes in lymphomas3, 4. This evidence concerns the gene ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive.